Fire detecting system



March 10, 1942. F, C EVANS 2,275,949

FIIRE DETECTING SYSTEM Filed March 4, 1938 2 Sheets-Sheet 1 INVENTOR" F.C. EVANS ATTORNEY 2 Sheets-Sheet 2 Filed March 4, 1958 INVENTOR F. C.EVANS BY ATTORNEY Patented Mar. 10, 1942 'FIRE'DETECTING SYSTEM Francis0. Evans, Staten Island, N. Y., assignor to AmericanDistrict TelegraphCompany, New York, N; Y.', a corporation of New Jersey Application March4, 1938, Serial-No. 193,878

7 Claims.

This invention. relates toralarm or control systemsfor the supervisionor detection of fire conditions in installations where large normaltemperature changes are encountered. A sensitive alarm or control systemmay respond to normal or safechanges in temperature for which analarm isunnecessary and not desired. For example in the protection ofa premisesor enclosure which is heated by blower heaters or similar heating meansit is found that the rate of rise alarm system will occasionally cause afalse alarm-when a heater is turned on.

In prior systems it has been proposed that the system should be renderedinoperative during changes of temperature due to blower heater operationand therefore inoperative to an extent that the system will notsupervise a fire condition thereby failing completely in its inendedpurpose. Correction of this fault has been obtained in prior aero-tubesystems by venting the system during normal and safe temperaturevariations sothat pressure can not be built up or by using an extremelyhigh critical operating temperature for sending an alarm.

It is an object of this invention to provide a supervisory alarmsystemwhich will not respond to normal changes of temperature but will stillbe operative to detect a fire condition by providing a device which willchange theoperating characteristic of the alarm system.

It is a further object of this invention to provide an aero-tube system,in connection with an alarm system. wherein'the pressure at which analarm is given can be changed in response to a local heat sourceso thatwhen it creates a rapid change-of temperature an abnormalcritical'pressure in the-aero-tube will be necessary before an alarmwill be given.

Another object ofthis invention is to provide anaero-tube supervisorysystem wherein changes in pressurein said aero-tube system due to normaltemperature changes will change the characteristics of an electriccircuit to thereby inhibit an alarm due tosuch changes but stillpermitting an alarm to be given in the event of ccurrence of a fire.

Still another object of this invention is to provide a rate oftemperature rise supervisorysystem in which one set ofcontacts-is-provided for. operation. in an alarm circuit at abnormaltemperatures while another set of more widely spaced contacts aresubstituted when a blower heater is started.

A further object of this invention is to provide alarms are prevented byisolating the section. of aero-tube subject to rapid rate of rise intemperature and utiliziing a. differential valve to by.-

' pass pressure pulses resulting from fire condian aermtube supervisorysystem: whereinfalse tions to thereby cause an alarm.

A. further object of this invention is tov provide a. pressure tubesystem in connection with an alarm system in which the pressure isallowed to change due to any change of temperature but-wherein falsealarmsare prevented.

Further objects and advantages of this invention will appear from thefollowing description of the several preferred embodiments thereof shownin the accompanying drawings, wherein Fig. 1 shows the generalarrangement of. this invention in an enclosure;

Fig. 2 shows a detailed arrangement of the preferred embodiment of thisinvention;

Fig. 3- shows a modification of theinvention disclosed in Fig. 2;

Fig. 4 shows the detail of a diiierent modification of this invention;and

Fig. 5 shows another modification: of this invention.

Fig. 1 of the drawings shows an enclosure wherein an aero tube firedetecting system is arranged to detect a fire condition and is also soarranged that a blower heater may so affect the aero'tube system that afalse fire alarmcondition may exist. Aero tube I is shown arranged inthe usual manner on the ceilings of two different rooms for firedetection and connected to an alarm or supervisory contact device 4while the blower heaters 2 and 3 are located in close prox- Fig. 2- ofthe drawings shows the preferred embodimentof devices 4 and 4' of Fig. lfor altering the characteristics-of the supervisory system wherebynormal changes in temperature in the enclosiue will change the operatingcharacteristics of the aero tube circuit to prevent false As in Fig. 1,the aero tube 1 serves to alarms. detect a fire conditionand tocreateanalarm through themate of rise inpressure in said tube;

the usual compensating vents 22 being provided to equalize the pressuresinside and outside of the tube for gradual temperature changes. Theblower 2 is arranged to direct hot air on a control device 4', such asis shown in Fig. 1. This device comprises an outer enclosure in which islocated an expansion chamber 5. The expansion chamber 5 is connected toaero tube 8 and branches I and II thereof. These branches are in turnconnected to bellows I2 which control a bridge member I5. The bridgemember is adapted to support adjustable electrical contacts I8, saidcontacts being connected to alarm circuit I9 and 20. Contacts I6 arearranged to cooperate with contacts I8. said contacts I6 being controlled by bellows I4 which are in turn controlled by the aero tube I.

The operation of this system is designed to neutralize the normal andrapid changes in temperatures in an enclosure to prevent a false alarm.In order to accomplish this result the spacing of contacts I6 and I8 isvaried in such a manner that during normal or safe changes intemperature a closure of said contacts is prevented. This isaccomplished when the control device 4' is actuated by the blower heaterto cause expansion of the air and consequently an increase of airpressure to be transmitted through the tubes 3, III and II to bellowsI2, which in turn lift the bridge member I 'to increase the separationbetween contacts I6 and I8. Thus when a fire condition occurs the aerotube I will respond in its usual manner even though the blower 2 hasjust come on and causes what might normally be an operating increase intemperature. The pressure in the aero tube will increase in response toa fire condition sufficiently to close the contacts I6 and I8, therebyclosing the alarm circuit I9 and 20 to operate the bell 23. Of coursethe situation may arise where another blower heater may also affect thesame aero tube system. In this event another control device 6 will beprovided and connected to the first control device 5 through the tube 6.Thus in the event that another blower heater 3 is turned on, the aerotube system will be in condition to prevent false alarms and to stillrespond to the fire condition.

Fig. 3 shows a modification of the control device 5 shown in Fig. 2wherein a solenoid 30 and its armature 28 are adapted to generat apressure in tubes 8, I0 and II by compressing a bellows 26. Thus whenthe blower heater motor is turned on, the circuit to solenoid 30 iscompleted and it operates in the obvious manner to increase the pressurein tubes 8, ID and II to thereby lift the bridge I5 in the same manneras the device 5. Therefore the false alarm is prevented and the aerotube system is still maintained responsive to a fire condition.

Fig. 4 shows another modifications of this invention wherein closure ofthe motor circuit again changes the characteristics of the aero tubesystem to prevent a false alarm. 2'! indicates a relay connected throughconductors 35 and 31 to the motor circuit of blower 2 said relay beingadapted to control the alarm circuit, including the conductors I9 and 2Dand the bell 23. Relay 21 also controls the spacing of contacts whichare in turn responsive to the aero tube I. For normal operation of aerotube I, aero-detector unit I4 is controlled by said aero tube. Thisaero-detector comprises two control chambers 9 and I3 which in turnoperat the bellows IT.

The bellows support the contacts I6 which are in turn adapted tocooperate with contacts l8 to control the alarm circuit I9 and 20. Onechamber 9 is connected to one end of the aerotube while chamber I3 isconnected to the other end of the aero-tube, each chamber having vents22 which release minor changes in pressure within the aero-tube such asthose usually caused by slow changes in temperature where no blowerheaters are present. Thus in the absence of the blower heater operationa fire condition will cause expansion of the air in the aero tube to inturn operate the bellows I! and close contacts I6 and I8. Contacts I6and I8 close a circuit through conductor I9, relay armature 28, bell 23and battery 24 to give a fire alarm. In th event that the blower motoris turned on by closing switch 32, a new detector unit I4 is thrown intothe aero tube circuit by means of relay 2'! which is energized by themotor circuit. The new detector having chambers 9 and I3 is connectedthrough tube 1 to the main aero tube I, this detector unit being similarin construction to unit I4 mentioned heretofore. The only difference inthis detector unit is that the spacing between contacts I6 and I8 ismuch wider than the spacing between contacts I6 and I8, the result ofwhich is that a much higher pressure is required in tube I to close thecontacts and thereby 0perate the alarm 23. Thus when a blower heatermotor is turned on by switch 32, a potential is impressed on relay 2'!which operates armature 28 against spring 29 to thereby substitutecontacts I6 and [8 for I6 and I8 which are normally in the alarmcircuit. Now when a fire condition occurs the increased pressure in theaero tube I will operate the more widely spaced contacts I6 and I8 tooperate the alarm 23. However, operation of the blower heater will notcause suflicient pressure to develop in the aero tube system to. closethe widely spaced contact gap.

Fig. 5 shows a further modification of this invention which embodies adifferent principle of operation in that the aero tube I is allowed togenerate a high pressure due to a fire condition to thereby operatedifierential valves 4| which in turn connect the increased pressure tothe aero-detector unit I4 and thereby cause operation of the alarm 23.As shown above in Fig. 4 the motor circuit will cause operation ofsolenoids 30. However, these solenoids are arranged to operate armatures3| and valves 40 in the aero tube I and thereby isolate the local aerotube section I which is affected by the blower heater 2. Valves 40 maybe by-passed by differential mercury valves as shown at 4|. A differenttype of fire detecting unit is used in connection with the aero tube I.This unit may comprise a bellows 42 and a bimetallic element 43, saidbimetallic element being adapted to compress bellows 42 under abnormalheat conditions. In normal operation a fire'condition anywhere in theenclosure protected by aero tube I and I will operate the detector unitI4 to close contacts I6 and I8 and thereby operate the alarm 23.However, when a blower heater switch 32 is closed, the blower heaterwill start up and the solenoids 30 will operate to close valves 40. As aresult aero tube I is left in condition for normal operation whereas thesection I is isolated from tube I and will not operate in response tothe blower heater 3 and can respond to a fire conditiononly with the aidof the devices 42. These detector units 42 are operated by thebimetallic elements 43 to increase the pressure in theaero tube I tosuch an extent,

that difierential valves 4! will operate. The bimetallic element isadjusted to operate at a temperature in excess of the maximumtemperature of the blower heater so that its operation will not becaused by the blower heater but may be caused by a fire conditionsuperimposed on the blower heater operation. The differential valves 4|are constructed as shown in the drawing and filled with mercury to thelevels indicated therein so that abnormal pressure of the aero tube I'will force the mercury from the well 44 over into the tube 45 to therebyallow transfer of.

pressure from tube to tube l, which pressure in turn operates thebellows I! of the detector l4 and thereby closes the circuit |92B togive a fire alarm.

From the above description of the different modifications of thisinvention it is apparent that false alarms are prevented whilemaintaining the system operative to respond to fire conditions so thatthe premises is always protected. Prior art systems are known to preventfalse alarms but it is believed that none of them presents theadvantages of this system wherein the system is always maintained inoperative condition to respond to an actual fire condition.

I claim:

1. In combination, an enclosure, a heating source therein, an aero-tubefire detecting system arranged to operate after a predetermined increasein pressure therein, pressure operated contact means adapted to beoperated by said aero-tube system, pressure operated bridge means forspacing said contacts, an acre-tube system connected to control saidbridge and a chamber positioned to be affected by said heating sourceand connectedto said control aero-tubesystein for changing the gaspressure in said control aero-tube system in response to said heatingsource to thereby change th spacing of said contacts when said sourcegives ofi heat.

2. In combination, an enclosure, a heating source therein, an aero-tubefire detecting system arranged to operate after a predetermined increasein pressure therein, pressure operated contact means adapted to beoperated by said aero-tube system, pressure operated bridge means forspacing said contacts, an aero-tube system connected to control saidbridge, a bellows connected to said control aero-tube system andelectromagnetic means actuated when said heating source operates foractuating. said bellows, and increasing the pressure in said controlaerotube system to operate said bridge and change the spacing of saidcontacts to delay their closure.

3. In combination, an enclosure, a heating source therein, an aero-tubesystem arranged to supervise temperature changes in said enclosure andto operate upon a predetermined increase of pressure in said aero-tube,an alarm circuit, contacts therein, means connected to said aero-tubesystem for closing said contacts, a second set of contacts havinggreater spacing than said first mentioned contacts, contact closingmeans connected to said acre-tube system in parallel with said firstcontact closing means for controlling said second set of contacts upon arise in temperature due to operation of said heating source and switchmeans operated when said heat source operates for connecting said secondset or" contacts to said alarm circuit and disabling the first set ofcontacts.

l. In combination, an enclosure, a heating source therein, an aero tubesystem to supervise temperature changes in said enclosure and to operateon a predetermined rate of rise of tem-v perature, an alarm circuit,contacts therein, pressure controlled means in said system for closingsaid contacts, a second set of contacts having greater spacing than saidfirst mentioned contacts, pressure controlled means in said system forclosing said second contacts and switch means operated when said heatsource operates for connecting said second set of contacts to said alarmcircuit and for disabling the first contacts.

5. In combination, an enclosure, a heating source therein, an aero-tubesystem arranged to supervise temperature changes in said enclosure andto operate upon a predetermined rate of rise of temperature, an alarmcircuit, means for operating said alarm circuit at a predeterminedpressure in said system, means connected to said aero-tube system forcontrolling said first men-- tioned means, a second means for operatingsaid alarm circuit at a difierent pressure in said system and means insaid system for controlling said second means, and switch means operatedwhen said heat source operates for connecting said second operatingmeans to said alarm circuit and for disabling the first means foroperating said alarm circuit.

6. In combination, an enclosure, heating means in said enclosure, a firedetecting system comprising an aero-tube circuit and pressure oper-'ated means therein for detecting a predeterminedrate of rise oftemperature in the enclosure, an alarm circuit, means including saidpressure operated means for initiating operation-of the alarm circuit attwo different pressures in said aero-tube circuit, and means operativelyassociated with the heating means for preventing operation of the alarmcircuit at the lower of said two pressures when the heating means isoper-.

